In order to reduce the moisture brought into the purifier (or dryer) by the heating gas and ensure the service life of the purifier (or dryer), the heating pressure of the purifier should be controlled to the normal working pressure (2MPa). In addition, the gas flow velocity in the purifier is inversely proportional to the pressure. The amount of rising steam in the lower column and the amount of condensation in the condensing evaporator are reduced, which also has a certain influence on the distillation condition of the column; After the switch over of the accumulator (or the switch over heat exchanger), the liquid air deposited in the backflow sewage nitrogen vaporizes due to the pressure reduction. The latent heat of vaporization should be absorbed during the evaporation of liquid air, which makes the temperature of backflow sewage nitrogen lower, which expands the temperature difference at the cold end and is not conducive to self removal;
The change of temperature in the middle of air separation plant is the result of many factors, and after taking measures to adjust, it will change other working conditions related to it. Therefore, we should have an overall concept for the adjustment of temperature in the middle of accumulator (or switching heat exchanger) to prevent isolated and one-sided view. We should make a comprehensive analysis of the influencing factors, grasp the main contradictions and take effective measures. There is also a problem of "distribution of cooling capacity" closely related to "storage cooling capacity" of air separation plant manufacturers. We hope that the remaining cooling capacity after offsetting the cooling loss will be kept in the distillation column system (including subcooler and liquefier) as far as possible for liquefied air.
Air separation plant manufacturers usually keep the pressure of air cooling tower and water separator higher (0.4MPa), and avoid excessive pressure fluctuation, and then throttle through valve. 3 MPa. In this way, the water content in the purge gas is unsaturated, which is more conducive to remove the residual water in the equipment pipeline before the accumulator. High heat transfer efficiency, large heat transfer area per unit volume, about 2500 m3 / m3. Moreover, due to the direct heat exchange between cold and hot fluids, it is basically a stable heat transfer process, which can ensure the stability of working conditions in the tower. The temperature of air flow and packing in the accumulator will change periodically with the switching time, which is an unstable heat transfer process;
The heat exchange incomplete loss Q2 (or Q2) of air separation plant manufacturer. The cooling capacity of low temperature gas is recovered by each heat exchanger in the device. Ideally, the low temperature backflow gas leaving the unit should be reheated to the same temperature as the positive flow gas entering the unit. That is to say, only when the temperature difference at the hot end reaches zero can all the cold energy be recovered. However, heat can only be transferred from high-temperature objects to low-temperature objects. In order to transfer heat from high temperature material to low temperature material in heat exchanger, there must be temperature difference. The temperature difference △ t at the hot end reflects that the temperature of the low temperature gas in the unit is lower than that of the air entering the unit, that is, the cooling capacity cannot be fully recovered, and the cooling capacity loss is called "incomplete heat exchange loss". It is proportional to the temperature difference.
If the compression pressure of liquid oxygen is higher than the critical pressure (for example, the oxygen pressure for chemical industry is 6.0MPa or higher), there is no gasification stage with constant temperature in the gasification process of heat exchanger. This will affect the heat transfer performance of high-pressure heat exchanger, which should be fully considered in the design. The air separation plant manufacturer increases the expansion through the liquefier. The expanded gas flows directly to the cold end of the switching heat exchanger; The other way is through the liquefier. If the gas flow through the liquefier increases, the cooling capacity is sufficient, and the flow rate increases, the heat transfer can be enhanced, and the liquefaction capacity can be increased. Therefore, the bypass valve should be turned down to let more gas pass through the liquefier.
